The flight-proven General Purpose Heat Source Radioisotope Thermoelectric Generator (GPHS-RTG) may use the heat from the radioactive decay of 238Pu included in eighteen stacked General Purpose Heat Source (GPHS) Modules. At the beginning of life (BOL), the GPHS-RTG may have a unit power output of approximately 290 Wdc. The typical weight of the GPHS-RTG may be about 56 kg, resulting in a specific power (e.g., power density) of approximately 5.2 W/kg. With a nominal thermal power of 250 Wth of a GPHS module at the BOL, the GPHS-RTG may have a system efficiency of approximately 6.7%. The GPHS-RTG has powered large space exploration missions (e.g., Ulysses, Galileo, and Cassini) launched in the 1990's decade, as well as the New Frontier class Pluto-New Horizons mission in 2006.
Since the mission in 2006, space programs (e.g., National Aeronautics and Space Administration (NASA)) have focused efforts on developing smaller Radioisotope Power Systems (RPS) with multi-mission capabilities, including capability of operation in Space and in planetary atmosphere environments. For example, an Advanced Stirling Radioisotope Generator (ASRG) may provide higher fuel efficiency relative to a comparable Radioisotope Thermoelectric Generator (RTG). Due to a limited inventory and future production rate of 238Pu, there may be increased incentive to use the ASRG unit. However, the nominal power output of the ASRG may limit its application to lower power missions. To compensate, additional ASRG units are typically required to meet higher power applications.
Therefore, it is desirable to develop a common platform modular Stirling radioisotope generator that can meet multi-mission power requirements.